Loaded dimensionA BUILD READER HAS ASKED WHAT IS THE CORRECT LOADED DIMENSION FOR A LINTEL SUPPORTING A HIP ROOF. THE CORRECT ANSWER IS: IT DEPENDS.

DESIGNRIGHT

LOADED DIMENSIONS FOR NZS 3604:2011 LINTELS

Actually, it depends on quite a lot of things, but

the most important question to ask is whether

it is to be a stick-framed roof or a trussed roof?

Once this is answered, the best way to work out

the loaded dimension (LD) for the lintel is to use

the following rules of thumb.

Stick-framed roofThe loaded dimension for a lintel in a stick-

framed roof is half the distance (D1 or D2 in

Figure 1) from the wall corner to the far end of

the lintel. Then use NZS 3604:2011 Timber-

framed buildings lintel tables to get its size.

Trussed roofFor a lintel in the hip end wall of a trussed roof

(Lintel 1), the loaded dimension is half the

distance from the end wall to the girder truss or

truncated girder truss (see D1 in Figure 2).

A lintel in the side wall (Lintel 2) is more

complex as it is likely to have a girder truss landing

on it. There are a lot of variables making it difficult

to determine the load from the girder truss.

NZS 3604:2011 lintel tables don’t provide for

concentrated loads on lintels, so ask the truss

supplier for a lintel size by specific engineering

design (SED) as part of the roof package.

Stick-framed roof.Figure 1

BY ROGER SHELTON, BRANZ SENIOR

STRUCTURAL ENGINEER

D1D2

Lintel 1

Lintel 2

Note: Ceiling framing omitted for clarity.

Loaded dimension (LD) of:

D2

D12

2

● Lintel 1 =

● Lintel 2 =

The loaded dimension is a measure of

the weight of the construction that contributes to the

member under consideration.

30 — Build 133 — December 2012/ January 2013

Trussed roof.Figure 2

D1

Lintel 1

Lintel 2

girder truss (truncated shown)

Loaded dimension (LD) of:

● Lintel 1 =

● Lintel 2 by SED

D12

jack truss

Build 133 — December 2012/ January 2013 — 31